n. Slang term derived from the Freight or Chow wagons used in the late 19th century. These were often the last wagons in a wagon train, making them the least favorable to drive due to the dust, waste, and debris from the front of the train.

When used as in insult it refers to one's lack of intelligence, implying the insultee is capable of no more than operating a Chow wagon.

A useless piece of equipment, usually military, used to refer to a mule-drawn freight wagon which had been pieced together from dicarded or substandard parts, and subject to frequent breakdowns. Jackwagons typically were good for only one or two uses, then abandoned or discarded along roadsides and in ditches, and were often re-cannibalized to create new jackwagons.

"Maybe we should trot on over to mambypamby land and get you som confidence - you jackwagon!" Geico commercial